Amazon Web Services (AWS) powers everything from scrappy startups to Fortune 500 giants. So, AWS interview questions are relevant for all kinds of roles, from infrastructure design to cost governance.
Now, while some interviews test definitions and acronyms, the best ones dig deeper. They explore how well you understand AWS trade-offs—think of performance vs. cost, scalability vs. complexity, or security vs. usability.
In this guide, we’ll walk through foundational, intermediate, and advanced AWS interview questions. We’ll also share real-world scenario prompts that challenge you to think like the pro AWS cloud engineer you actually are.
Along the way, we’ll share how tools like CloudZero can help you not only answer those questions but back them up with cost-aware decisions.
Prepping For A Big AWS Interview? Start Here
An AWS interview takes more than memorizing service definitions. Interviewers want to see how you think through scalability, security, cost efficiency, and real-world architectural trade-offs.
Here’s how to prepare like the pro you already are:
Know the core AWS services cold
You don’t need to memorize every service. But you do need fluency in core building blocks like Amazon EC2, S3, VPC, IAM, RDS, and CloudWatch. Know what they do, when to use them, and how they integrate.
Keep your prep relevant, too. If you’re targeting an AI/ML-heavy role, for instance, you’ll want to dive deeper into tools like Amazon Bedrock.
Practice designing real-world architectures
Expect whiteboard or virtual design interviews. You’ll need to architect solutions on the fly. So, practice designing highly available, fault-tolerant, and cost-optimized systems.
Just as important, be ready to explain your choices, especially when it comes to trade-offs between performance and cost. It says you know what and why you are doing it.
Prepare for scenario-based and behavioral questions
Interviewers often ask:
“How would you migrate a legacy app to AWS with minimal downtime?”
“You notice EC2 costs have spiked. What do you do?”
So, practice thinking through these scenarios out loud.
You can use CloudZero’s blog or FinOps resources to learn how engineers tie usage to cost insights — a powerful angle to bring up during interviews. Why? Because reducing cloud waste is a top priority for most organizations today. It’s a $44.5 billion problem, according to the FinOps Foundation.
Credit: FinOps Foundation’s Key Priorities Shift Report
Brush up on security and cost optimization best practices
Understanding IAM roles, least privilege access, and encryption options is non-negotiable as well. But don’t forget about cost visibility and optimization strategies, like using Savings Plans, choosing the right instance types, and avoiding unnecessary data transfer costs.
Use hands-on labs and cert study guides (yes, even if you’re not taking the exam)
Platforms like AWS Skill Builder, ACloudGuru, and free-tier AWS accounts let you get hands-on experience. This is a solid way to retain your AWS knowledge. Even AWS certification prep materials can help structure your study.
Something else. If you’re aiming for a senior or leadership role, be ready to speak to cloud cost governance, AWS budgeting tools, and how you balance innovation with financial accountability.
Knowing tools like AWS Budgets, Cost Explorer, and CloudZero can make your answers stand out.
Quick Overview Of The AWS Landscape (And Why AWS Know-How Is So Crucial Now)
AWS continues to dominate the cloud services market with about a 32% share. But AWS is broad, with over 240 fully featured services. These cover compute, storage, networking, databases, AI/ML, analytics, security, developer tools, cost management, and more.
This breadth gives teams enormous flexibility. But it also introduces complexity. And with it, the risk of surprise cloud costs and waste.
That’s why AWS expertise is in such high demand.
Engineers are expected to know how to deploy scalable systems. Architects must balance performance with resilience. Finance leaders also increasingly want engineers who can build cost-aware systems from the ground up.
Related read: 5 DevOps Skills Every Engineer Should Have In The Cloud Era
For employers, asking good AWS interview questions is a tested way to evaluate how candidates:
- Think through technical trade-offs
- Design for cost, scalability, and security
- Understand cloud-native patterns
- Know when not to over-engineer (a.k.a. overspend)
The good news? You don’t need to know everything. But you do need to understand the most relevant services, patterns, and decisions for your role. And that includes how they relate to your organization’s bottom line.
Once you’ve got your prep strategy locked in, it’s time to tackle the actual interview questions, starting with the essentials.
AWS Foundational Questions
These questions test whether you understand key AWS services, how they work, and how to use them productively.
What is Amazon EC2?
Answer: The Amazon Elastic Compute Cloud (EC2) service provides scalable compute capacity in the AWS cloud. It enables you to run virtual servers (called instances) in different configurations. Think of instance types, OS, networking, storage, etc..
Key features include auto-scaling, instance types for various workloads, and pay-as-you-go billing. It also includes elastic IP addresses, placement groups, and integration with other services like IAM and EBS.
Why this question:
It checks your grasp of the cloud-based compute resources. EC2 is arguably the backbone of AWS. So, your answer reveals whether you understand how to tailor instance types to workload needs, influencing both performance and cost optimization.
When would you use Amazon S3?
Answer: Amazon Simple Storage Service (S3) is an object storage service. It offers high availability, scalability, and durability (99.999999999%). It is also ideal for storing unstructured data such as backups, log files, media, or static assets for websites.
You can optimize S3 costs by choosing different S3 storage tiers based on access frequency (like S3 Standard, Infrequent Access, Glacier, etc). See more about how Amazon S3 object storage and pricing work here.
Why this question:
It’s testing your understanding of AWS’s scalable object storage and choosing cost-effective storage tiers.
What’s the difference between a security group and a network ACL?
Answer: A security group acts as a virtual firewall at the instance level. This allows or denies inbound/outbound traffic. It is stateful, meaning return traffic is automatically allowed. A network ACL (Access Control List) works at the subnet level and is stateless, meaning you need to explicitly define return traffic rules.
Why this question:
The interviewer wants to know if you understand AWS security layers and best practices.
What is IAM, and is it even important?
Answer: AWS Identity and Access Management (IAM) enables you to manage access to AWS services and resources securely. It lets you define users, groups, roles, and permissions, applying the principle of least privilege.
Why this question:
It’s gauging your security posture, operational discipline, and awareness of access management in shared environments.
What is the AWS Shared Responsibility Model?
Answer: The shared responsibility model outlines AWS’s role in securing the infrastructure (hardware, software, networking, and facilities) and the customer’s role in securing their applications, data, configurations, and credentials.
Why this question:
It is meant to see whether you can draw the line between AWS’s accountability and yours.
What is an AWS Availability Zone, and why are they important?
Answer: An Availability Zone (AZ) is a physically separate data center in a region, with independent power, networking, and cooling. AWS regions contain multiple AZs to support fault-tolerant and high-availability architectures.
Also see: What Are AWS Regions (And How They Affect AWS Cloud Costs)?
Why this question:
Understanding AZs is crucial for designing resilient, highly available systems (disaster recovery and latency optimization).
Intermediate Questions
So, you’ve nailed the basics. Interviewers often move into questions that test your practical understanding of how AWS services work together, especially in production environments.
How does Auto Scaling work in AWS, and when should you use it?
Answer: AWS Auto Scaling automatically adjusts compute capacity based on demand. You define scaling policies (like target CPU utilization or scheduled scaling), and AWS launches or terminates EC2 instances accordingly. It works with services like EC2, ECS, DynamoDB, and Aurora.
So why this question?
This tests your ability to build resilient, cost-efficient applications that can scale up during peak usage and scale down during off-peak hours.
What’s the difference between a Reserved Instance and a Savings Plan?
Answer: Reserved Instances (RIs) offer a significant discount over On-Demand pricing in exchange for a one- or three-year commitment to a specific instance type, region, and OS. Savings Plans offer similar discounts but with more flexibility. SPs cover EC2, Fargate, and Lambda usage in a broader scope, based on hourly spend rather than instance type.
Why this question:
The goal here is to see if you can choose the right commitment model based on workload stability without sacrificing long-term cost control.
What is the difference between Security Groups and IAM roles?
Answer: Security Groups control network-level access to resources (like which IPs can access EC2 instances), while IAM roles manage who can do what within AWS. That includes permissions for users, services, or applications to access specific resources.
Why this question:
This question checks whether you can distinguish between network access controls and identity-based permissions.
When would you choose RDS over DynamoDB?
Answer: Choose Amazon RDS for structured, relational data that requires SQL support, complex joins, or ACID transactions. Choose DynamoDB for high-throughput, low-latency workloads with flexible schema needs (e.g., IoT, gaming, session data), especially if scalability is a priority.
And why this question?
This evaluates your ability to select the right database for the job, which affects performance, scalability, and DB costs.
How does CloudFormation help with infrastructure management?
Answer: AWS CloudFormation enables infrastructure as code (IaC). It lets you define and provision AWS resources using YAML or JSON templates. It also automates deployments, ensures consistency, and supports version control.
Why this question:
IaC is foundational for modern DevOps best practices. Your answer will show you’re familiar with automating infrastructure in a scalable, auditable, and repeatable way.
What’s the difference between public and private subnets in a VPC?
Answer: A public subnet has a route to the internet via an internet gateway. It allows external communication. A private subnet does not. Instead, it can only access the internet through a NAT gateway or NAT instance, usually for backend or sensitive resources.
Why this question:
This question checks your understanding of designing secure and scalable environments in VPCs.
You’ve made it this far. Now time to go deeper.
Advanced AWS Interview Questions And Concepts
This is where interviewers probe technical depth. They also want to see architectural decision-making ability, often under constraints. If you’re interviewing for a senior cloud engineer or DevOps lead or solutions architect role, expect a few of these to come up, often in follow-ups to scenario-based ones.
How would you design a multi-region, highly available web application in AWS?
Answer: Use Route 53 with latency-based routing and health checks to route traffic across regions. Deploy your application across multiple AWS regions using services like ELB, EC2 Auto Scaling, and RDS Multi-AZ or Amazon Aurora Global Databases. Use S3 cross-region replication for static assets and replicate state/data where necessary. Consider caching with Amazon CloudFront and storing session state in DynamoDB Global Tables.
Why this question:
It tests your ability to design for fault tolerance and global availability. That, while managing latency and potential data consistency trade-offs.
What are the trade-offs between using VPC Peering and AWS Transit Gateway?
Answer: VPC Peering is simpler and cheaper for connecting a small number of VPCs. However, it lacks centralized control. It also scales poorly as connections grow. AWS Transit Gateway offers centralized routing between multiple VPCs and on-premises networks. And this simplifies management and scalability, but at a higher cost.
So, why this question?
It shows if you can scale infrastructure thoughtfully while understanding cost, complexity, and operational overhead.
How would you reduce AWS data transfer (egress) costs across regions and to the internet?
Answer: Options include:
- Using CloudFront to cache and serve static assets closer to users,
- Leveraging S3 Transfer Acceleration for uploads,
- Consolidating inter-region traffic via centralized services,
- Using private inter-region links when applicable, and
- Minimizing unnecessary cross-region traffic by architecting data-local solutions.
Why this question matters:
Your answer will express your understanding of architecting for cost efficiency, especially in distributed systems.
How does AWS Organizations help manage multiple accounts at scale?
Answer: AWS Organizations lets you group and centrally manage multiple AWS accounts. You can apply Service Control Policies (SCPs), consolidate billing, delegate permissions, and segment teams or business units.
Why this question:
Organizations promotes better security, budget tracking, and operational control.
How would you monitor and troubleshoot performance in a serverless application using AWS Lambda?
Answer: Use AWS CloudWatch Logs, CloudWatch Metrics, and X-Ray for tracing function execution and latency. Enable Lambda insights for runtime-level performance data. Monitor cold starts, throttle rates, and downstream service latencies (like DynamoDB or SQS).
Why this question matters:
Serverless isn’t maintenance-free. So, this question tests whether you can ensure observability and performance in modern event-driven architectures.
What’s your approach to cost optimization in AWS without sacrificing performance
Answer: Strategies include:
- Rightsizing EC2 instances,
- Using Savings Plans or Spot Instances,
- Enabling Auto Scaling,
- Selecting the right storage tiers,
- Leveraging AWS Lambda for spiky workloads,
- Consolidating traffic with CloudFront, and
- Using tools like CloudZero for real-time cost intelligence.
Why this question:
This question blends engineering and FinOps. It’s about designing solutions that serve both performance goals and budget constraints. It’s an opportunity to highlight practical tools and processes you’ve used, too!
How do you secure sensitive data in transit and at rest in AWS?
Answer: For data in transit, use TLS (HTTPS) for secure communication between services, and enforce encryption on services like API Gateway, ELB, and CloudFront. For data at rest, enable server-side encryption (SSE) with AWS Key Management Service (KMS) on services like S3, EBS, RDS, and Redshift. Use customer-managed keys (CMKs) for tighter control, auditability, and key rotation.
Related read: Amazon Redshift Pricing Guide – Without The Usual Jargon
And why this question?
It is testing your ability to design systems that meet compliance and security standards (like HIPAA, SOC 2, or GDPR). Something to do with AWS zero-trust security models as well.
How would you architect a cost-effective data pipeline for processing terabytes of data daily in AWS?
Answer: Use Amazon Kinesis Data Streams or AWS Managed Kafka for ingestion. Pick AWS Lambda or AWS Glue for lightweight ETL. Look to S3 as the landing zone or long-term storage.
Use Amazon Athena or Redshift Spectrum for querying data directly from S3, and partition data for performance. Apply lifecycle policies to move data to cheaper storage tiers like S3 Glacier Deep Archive.
Related read: Amazon Kinesis Pricing Explained
Why this question:
The answer reveals whether you can balance performance, scalability, and cost when working with big data.
Scenario-Based Questions
These questions follow your thought process, priorities, and problem-solving (balancing performance, innovation, and cost-efficiency).
Say you’re seeing unexpected spikes in EC2 costs. How do you investigate and resolve the issue?
Answer: Start by reviewing AWS Cost Explorer or CloudZero to identify which EC2 instances or accounts are driving the cost spikes. Check for untagged or mistagged resources, unused running instances, or unoptimized instance types.
Look at Auto Scaling Group activity and Spot instance usage. From there, consider right-sizing and switching to Reserved Instances or Savings Plans. Better still, consider replacing EC2 with containerized or serverless alternatives.
So, why this question?
A strong answer here shows you’re not just technical, but also business-aligned. The interviewer wants to see your cost awareness, troubleshooting skills, and ability to tie technical insights to financial outcomes.
You’re asked to migrate a monolithic on-premise application to AWS. Where do you start?
Answer: Start with an assessment phase: inventory the app’s components, dependencies, and data. Choose a migration strategy — typically “rehost” (lift-and-shift) as a first step using AWS Application Migration Service.
From there, identify services for refactoring (like RDS for the database, S3 for static content, EC2 or ECS for the app tier). You can use tools like AWS Migration Hub and AWS DMS for planning and execution.
Why this question:
It gauges whether you can create a migration roadmap that balances speed, risk, and cost. Bonus points to you if you include a phased modernization plan after rehosting.
How would you design a logging and monitoring solution for a distributed microservices app on AWS?
Answer: Use CloudWatch Logs and CloudWatch Metrics to collect service-level data. Enable X-Ray for distributed tracing across services. Aggregate logs into centralized storage (such as S3 or OpenSearch) for analysis. For containerized apps, integrate FluentBit or FireLens for log routing. Ensure logs are tagged by environment and service for better filtering and cost visibility.
Why this question:
It checks whether you can maintain observability and operational control as the system scales.
A product team wants to launch a new feature quickly. How would you help them deploy it safely and cost-effectively on AWS?
Answer: Propose a CI/CD pipeline using AWS CodePipeline and CodeDeploy or a GitHub Actions + Lambda setup. Use feature flags or canary deployments to minimize risk. Choose serverless components (like API Gateway + Lambda + DynamoDB) to reduce infrastructure management and scale on demand. Monitor usage and cost metrics closely after launch to evaluate your cloud ROI.
Why this question:
It highlights your ability to balance speed, safety, and cost while collaborating cross-functionally with your product and engineering teams.
Your app needs low-latency global content delivery. What AWS services are you using?
Answer: Use Amazon CloudFront as a CDN to cache and deliver content close to users. Store static assets in S3. Serve dynamic content via API Gateway or Lambda@Edge. Then get Route 53 for geo-based routing. If need be, integrate AWS Global Accelerator to improve global TCP/UDP performance.
Why this question:
It’s a test of your ability to build responsive, globally available systems — and whether you can optimize performance without running up AWS data transfer costs.
Your organization uses multiple AWS accounts for different teams. How do you manage permissions, billing, and compliance across them efficiently?
Answer: Use AWS Organizations to group accounts under a central management account. Apply Service Control Policies (SCPs) to enforce security boundaries. Enable consolidated billing for centralized cost management.
Use AWS Identity Center (formerly SSO) for federated user access. Integrate AWS Config and CloudTrail across accounts for compliance tracking and unified auditing.
Why this question matters:
This checks if you understand how to scale governance and security across growing cloud environments.
A CloudFormation deployment keeps failing, but you’re not getting detailed error logs. How do you debug and fix it?
Answer: First, review the CloudFormation Events tab for stack-level failure messages. Validate the template using the linter (cfn-lint) or the CloudFormation validate-template command. Check IAM permissions and resource quotas that may be blocking resource creation. If need be, enable stack rollback debugging or deploy resources manually to isolate the issue.
Why this question:
It is probing your patience, attention to detail, and comfort with diagnosing ambiguous or low-feedback AWS errors.
You’ve received alerts that a production API is responding slowly. What AWS tools and steps would you use to investigate?
Answer: Check CloudWatch metrics for increased latency or errors in the backend services (e.g., Lambda, ECS, or EC2). Use CloudWatch Logs for detailed request traces and AWS X-Ray for service-level tracing. Assess Auto Scaling activity, CPU/memory utilization, and throttling metrics.
Also, review recent deployments, configuration changes, or traffic spikes using CloudTrail or deployment logs.
Why this question:
This tests your ability to respond to real-time production issues with a structured debugging approach — and highlights how well you know AWS observability tools.
You’re tasked with reducing overall cloud costs, but you can’t disrupt ongoing development. Where do you start?
Answer: Begin with this free cloud cost assessment to understand where you are coming from. Follow up with a tagging audit to ensure cost allocation by team, service, or environment. Use AWS tools to identify underutilized or idle resources. Prioritize non-critical workloads for Spot Instances, and convert predictable usage to Savings Plans. Look at storage tiers and data transfer costs for quick wins. Communicate clearly with teams before making any impactful changes.
Why this question:
This reveals your ability to think like a FinOps-minded engineer — someone who balances cost efficiency with minimal disruption to product velocity.
What are some common challenges engineers face when working with AWS, and how would you mitigate them?
Answer:
- Service sprawl and complexity: Use Infrastructure as Code and documentation to standardize setups.
- Unpredictable costs: Set up budget alerts, track cost per environment, and use platforms like CloudZero for real-time spend visibility.
- Security misconfigurations: Enforce IAM best practices, regular audits, and automated policy enforcement via tools like AWS Config.
- Poor observability: Use CloudWatch, X-Ray, and OpenTelemetry integrations to surface metrics and logs across services.
- Over-permissioned access: Apply the principle of least privilege, use IAM Access Analyzer, and implement permission boundaries.
What’s with this question?
It is testing your real-world experience. For example, can you anticipate problems before they escalate? Or, can you work smarter in a platform that offers flexibility and complexity?
Take the Cost-Intelligent Approach to AWS — In Interviews, On The Job, And Beyond
Mastering AWS interview questions is about more than passing a technical screen. It’s also about showing that you can think like a cloud builder.
Yet, nailing how your architecture decisions impact spend, avoiding cloud waste, and proving the value of every engineering choice you make? That’s next-level.
Whether you’re preparing for your next role or leading a team of cloud engineers, technical skills alone aren’t enough anymore.
To be the most profitable AWS engineer in the room, you’ll need to understand the trade-offs — performance vs cost, availability vs complexity. Then, be able to make technical decisions that align with both engineering goals and business outcomes.
That’s where CloudZero delivers a serious edge
CloudZero gives engineering, finance, and product leaders a shared language around cloud spend. Expect granular insights like cost per project, per environment, per feature, per deployment, and beyond.
Whether you’re in the interview room or the boardroom, CloudZero empowers you to speak confidently about the business impact of every decision you make in AWS.
Don’t just take our word for it. Teams at Moody’s, MalwareBytes, and Coinbase already trust CloudZero to understand, control, and optimize their AWS spend. We‘ve just helped Upstart save $20 million in months. And you can, too. 
and see the impact for yourself. Risk-free.
The Cloud Cost Playbook
The step-by-step guide to cost maturity
